Some of hub units according to a related art include a covering member for protecting a sealing member from foreign substances such as muddy water and gravels for improving the resistance to foreign substances (see, for example, Patent Literature 1).
A hub unit (rolling bearing unit) described in Patent Literature 1 includes a hub constructed by a combination of a hub main body and an inner ring, and an outer ring disposed outside the inner ring. Besides, the hub unit further includes a sealing member disposed between the inner ring and the outer ring, and a covering member covering ends on a vehicle inner side (a vehicle body side) of the outer ring and the sealing member. The outer ring is supported on a suspension disposed on the vehicle body side with a plurality of rolling elements disposed between the outer ring and the inner ring. The hub main body is provided with a wheel mounting flange for mounting a wheel thereon.
The covering member includes a large-diameter cylindrical portion, an outer diameter side sidewall portion extending inward from an end on the vehicle inner side of the large-diameter cylindrical portion, and a middle-diameter cylindrical portion extending from an inner end of the outer diameter side sidewall portion toward the vehicle inner side. Besides, the covering member includes an inner diameter side sidewall portion extending inward from an end on the vehicle inner side of the middle-diameter cylindrical portion, and a small-diameter cylindrical portion extending from an inner end of the inner-diameter side sidewall portion toward a vehicle outer side. The large-diameter cylindrical portion is fit on the outer circumferential surface of the outer ring. An end on the vehicle inner side of the sealing member is surrounded by the middle-diameter cylindrical portion, the inner diameter side sidewall portion and the small-diameter cylindrical portion of the covering member. The covering member inhibits muddy water from splashing on and gravels or the like from hitting the sealing member and its surrounding portion.
Besides, the covering member is provided with a drain hole in a part thereof that is positioned at a lower end when used and corresponds to a portion extending across the middle-diameter cylindrical portion and the outer diameter side sidewall portion. A foreign substance such as muddy water having entered the covering member through, for example, a small gap between the large-diameter cylindrical portion of the covering member and the outer ring is discharged through the drain hole.